A critical component of understanding present and past distribution of the incense trees is the location of the Inter Tropical Convergence Zone (ITC). This zone is defined by the line where climate high and low pressure zones meet. In the early Holocene (ca. 8000 BP), note that the ITC line was located far into Northern Arabia. This suggests that current Dhofar-like conditions could have extended far into central Arabia at that time, producing a much larger incense zone.